Grooves are formed in the tread of a pneumatic tire for mounting to a vehicle to expel water between the tire and the road surface to outside of the ground contact surface when running on a wet road surface (see for example Japanese Patent Application Laid-Open (JP-A) No. 8-276708).
There are also demands to reduce the rolling resistance of pneumatic tires as part of a gathering momentum to raise fuel efficiency accompanying restrictions on exhaust gas emissions and rising oil prices.